An aftertreatment system comprises a particulate filter configured to filter PM possessing a predetermined, least effective size range included in an exhaust gas flowing through the aftertreatment system. A PM sensor assembly is positioned downstream of the particulate filter and includes a housing having an inlet, an outlet, a sidewall and defines an internal volume. A PM sensor is positioned within the internal volume. The housing is configured to redirect a flow of exhaust gas entering the PM sensor assembly around the PM sensor so that small particles included in the exhaust gas flow having a first size within or smaller than the predetermined size range are directed around the particulate matter sensor. Large particles having a second size larger than the predetermined size range impact the PM sensor. A controller is communicatively coupled to the PM sensor.